1. Field of the Invention
The present invention relates to a thin film magnetic head including a magneto-resistive effect element for reading a magnetic field intensity of a magnetic recording medium or the like as signals, as well as a method of manufacturing the same.
2. Description of the Related Art
As the surface recording density of a magnetic disk device has lately been advanced, there is a need for enhancing the performance of a thin film magnetic head. As a thin film magnetic head, a complex type thin film magnetic head has widely been used that has a structure of a reproducing head having a read-only magneto-resistive (MR) effect element (hereinafter also referred to as an MR element) and a recording head having a write-only magnetism conversion element layered on a substrate.
MR elements include an anisotropic magneto-resistive (AMR) element using the AMR effect, a giant magneto-resistive (GMR) element using the GMR effect and a tunnel magneto-resistive (TMR) element using the TMR effect.
The characteristics of a reproducing head should particularly be high sensitivity as well as high output. As a reproducing head that satisfies such requirements, a GMR head using a spin-valve type GMR element has already been mass-produced.
Moreover, a GMR element having a structure that allows a sense current to flow in the perpendicular direction (layering direction) relative to the surface of each layer constituting the GMR element, that is, a current perpendicular to plane (CPP) structure (a CPP-MR element) has been developed as a next generation element. A TMR element that has already been mass-produced and put into practical use falls under the category of CPP-MR elements as well.
An MR element is placed between upper and lower shield layers formed of soft magnetic metal films and is disposed in a manner of being sandwiched between insulating layers referred to as gap layers. The recording density of bit direction is defined by a shield gap (also known as read gap length) between the upper and lower shield layers. As the recording density has lately increased, there is an increased need for a narrow shield gap or narrow track for the reproducing element of a reproducing head.
In the thin film magnetic head containing such a magneto-resistive effect element, a bias magnetic field application layer is disposed on each of two sides of an MR element. This bias magnetic application layers allow application of a so-called vertical bias to a free layer constituting part of the element. As a result, the generation of noise can be suppressed, thus allowing the operation of detecting a predetermined external magnetic field.
As described above, however, the shield gap of an element has rapidly been narrowed. Accordingly, there is a need for novel thin film magnetic head structures that allow a vertical bias magnetic field to be efficiently applied to a free layer from a bias magnetic field application layer having a limited volume.
The prior art similar to or related to the present invention that allows efficient application of a vertical bias magnetic field to a free layer from a bias magnetic field application layer includes Japanese Laid-Open application number 2006-86275 and Japanese laid-open application number 2007-250085.
However, there are limits of effects to be achieved because the shape of an element or bias magnetic field application layer is designed or controlled in such conventional proposals. Accordingly, there remains a need for original technologies based on totally new ideas instead of technologies that are an extrapolation of the prior art.
The present invention was made in these circumstances. The object of the present invention is to provide a new thin film magnetic head structure that allows efficient application of a vertical bias magnetic field to a free layer from a bias magnetic field application layer.